Lecture 17 -Receptors & G-proteins

Lecture 17 -Receptors & G-proteins - Signal...

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Signal Transduction
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Signal Transduction Signal outside cell is recognized Transmission across membrane Effect inside cell
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Signal Transduction & Molecular Circuits A primary messenger (hormone-H) binds to the extracellular part of a  membrane-embedded receptor (R) The HR complex generates a second messenger inside the cell which  activates proteins that alter the biochemical circuitry inside the cell Then, mechanisms are activated to terminate the signal transduction  pathway
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Signal Transduction Molecular  Switches Membrane embedded receptor Proteins transmit information into the cell The Ras protein, like the G α  subunit of  heterotrimeric G proteins, cycles between an  inactive GDP-bound form and active form bound  to GTP Tyrosine kinase modules of some receptors  upon dimerization are activated by cross- phosphorylation. Phosphorylated tyrosines serve  as docking sites for adaptor and signaling  proteins which permit further propagation of the  signal. Net result is amplification, fidelity and diversity
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Signal Transduction
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What G-proteins can Do
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Common Second Messengers
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Adrenaline
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G-proteins-also known as GPCRs for G-protein coupled receptors Trimeric molecular amplifiers ( α , β , γ subunits, α and γ are lipid-linked thus membrane bound) Bind to 7-transmembrane receptors on the cytosolic side Receptor activation switch GTP for GDP disassociation of α from βγ
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G-protein activation of adenylate cyclase
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Lecture 17 -Receptors & G-proteins - Signal...

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